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gh-40440: Add a timeout parameter to tkinter wait_variable()#152619

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gh-40440: Add a timeout parameter to tkinter wait_variable()#152619
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serhiy-storchaka:gh-40440-wait-variable-timeout

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Misc.wait_variable() wraps the Tcl tkwait variable command, which blocks until the variable is written — with no escape if that never happens (e.g. the application is torn down before the setter runs), so the call can hang forever.

Add an optional keyword-only timeout argument (in seconds).
With a timeout the wait is reimplemented in Python on top of tkapp.dooneevent() and a variable trace: it returns True if the variable was modified, or False if the timeout elapsed first (or the application was destroyed while waiting).
Without a timeout the behaviour is unchanged (the native tkwait call, always returns True).

Without a timeout wait_variable() blocks forever if the variable is never
set, for example because the window that would set it was destroyed.  The
new keyword-only timeout parameter bounds the wait and returns whether the
variable was modified.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Documentation build overview

📚 cpython-previews | 🛠️ Build #33359415 | 📁 Comparing 3afa68b against main (c5043dc)

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3 files changed
± library/tkinter.html
± whatsnew/3.16.html
± whatsnew/changelog.html

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